1. Field of the Invention
The present invention relates to a control scheme for controlling a standby channel route for an active channel route established between an ingress node and an egress node of a GMPLS (Generalized Multi-Protocol Label Switching) network.
2. Description of the Related Art
In recent years and continuing, MPLS (Multi-Protocol Label Switching) as a technique that introduces the concept of label switching to the IP network to enable network operations using paths is being widely implemented. However, the MPSL technique is not limited to application to the IP network, and GMPLS (Generalized Multi-Protocol Label Switching) as a technique for enabling automatic dispersion in a TDM (Time Division Multiplexing) network such as the SDH (Synchronous Digital Hierarchy)/SONET (Synchronous Optical NETwork) or a path network including a wavelength switching network is being contemplated for standardization and application by organizations such as the CCAMP (Common Control and Measurement Plane)-WG (Working Group) OIF (Optical Internetworking Forum) of the IETF (Internet Engineering Task Force) and the ITU (International Telecommunication Union).
By implementing the GMPLS technique, path connection between different systems may be standardized, and efficient network operations may be enabled by BoD (Bandwidth on Demand) services for high speed path connection and unilateral management of multiple layers. In GMPLS, an MPLS header is attached to an IP packet, and the IP packet is transmitted within the network based on a label contained in the MPLS header. Such packet transmission mechanism is referred to as label switching. It is noted that various items such as a timeslot, a wavelength group, or fiber, for example, may be used as a label.
In the GMPLS, signaling, routing, and link management protocols are established, and a concept referred to as switching capability is used to define the capabilities of the protocols for path control in the IP network, L2 switching network, TDM network, wavelength switching network, and fiber switching network, for example. An extension of RSVP-TE (Resource ReSerVation Protocol-Traffic Engineering) describing procedures for establishing a path along a route may be defined as the signaling protocol. As for the routing protocol, procedures are described for flooding link states within the network (i.e., using a flooding mechanism to detect/determine the state of the network by releasing information held by transmission apparatuses included in the network throughout the network and compiling the information into a shared database, the act of the routing protocol flooding its transmission apparatus database being referred to as “advertisement”) and enabling each transmission apparatus to determine its link state within the network through automatic dispersion. The routing protocol may be an extension of OSPF-TF (Open Shortest Path First-Traffic Engineering) configured to enable flooding of link information of various types of path networks.
FIGS. 16 and 17 are diagrams illustrating examples of constructing a ring network and establishing paths with plural apparatuses having GMPLS functions. Specifically, FIG. 16 shows a configuration of a GMPLS network, and FIG. 17 illustrates a basic path establishing sequence.
The illustrated GMPLS network of FIG. 16 includes an input transmission path 50, transmission apparatuses 51-56 (#1-#6) with GMPLS functions, and an output transmission path 57. The transmission apparatuses #1-#6 are sequentially connected by transmission channels, and a path is automatically established to enable signaling using their GMPLS functions.
In the following, a basic path establishing sequence is described with reference to FIG. 17. It is noted that transmission apparatuses 51 (#1) through 54 (#4) shown in FIG. 17 correspond to the transmission apparatuses 51 (#1) through 54 (#4) shown in FIG. 16. In this drawing, an example is illustrated where paths are established between the transmission apparatuses 51 (#1) through 54 (#4) with the transmission apparatus #1 as the ingress node and the transmission apparatus #4 as the egress node. It is noted that a topology map of the network and band information of the transmission apparatuses are arranged into a database by the OSPF functions of the GMPLS and are shared by all the transmission apparatuses included in the network. Also, when at least one of the transmission apparatuses updates its internal database, it advertises its updated database to the rest of the transmission apparatuses so that the database shared by all the transmission apparatuses within the network may be synchronized.
According to the example of FIG. 17, paths may be established by the following procedures:
1. First, a path establishing command (signaling request) is input to transmission apparatus #1 corresponding to the ingress node (see arrow a of FIG. 17).
2. At transmission apparatus #1, route calculation is performed for calculating the shortest route from transmission apparatus #1 to transmission apparatus #4 based on the shared database. In the present example, the shortest route is determined to be route (1) shown in FIG. 16 (i.e., route passing the transmission apparatuses #1-#4 in this order).
3. At the transmission apparatus #1, the status of the band of a port forming route (1) is switched from “free” to “reserved” (see 51a of FIG. 17), and a path message (Path MSG) is transmitted to the rest of the transmission apparatuses #2-#4 forming route (1) (see arrows b-d of FIG. 17).
4. The transmission apparatuses #2 and #3 receiving the path message switch the statuses of the bands of designated ports from “free” to “reserved” (see 52a and 53a of FIG. 17) and transmit the path message to the next transmission apparatus.
5. The transmission apparatus #4 corresponding to the egress node switches the statuses of the bands of designated ports from “reserved” to “determined (in use)” (see 54a of FIG. 17), executes transmission apparatus path establishing processes (cross connection including switching), updates its own database, and transmits a reserve message (Resv MSG) to the transmission apparatus #3 (see arrow e of FIG. 17). When the statuses of the bands are switched from “reserved” to “determined (in use)”, the transmission apparatus #4 assumes that its internal data (database) have been updated and transmits an OSPF advertisement message to the rest of the transmission apparatuses for advertising the change in its internal database (see arrow i of FIG. 17).
6. The transmission apparatuses #3 and #2 transmit the reserve message in reverse order of the transmission order of the path message (see arrows f and g of FIG. 17). The transmission apparatuses #1-#3 receiving the reserve message switch the statuses of their corresponding bands from “reserved” to “determined”, execute cross connection (Xcon) processes (see 53b, 52b, and 51b of FIG. 17), update their own databases, and transmit OSPF advertisement messages for advertising the change in their internal databases to the rest of the transmission apparatuses (see arrows j-m of FIG. 17).
7. Overall cross connection of route (1) may be completed when the transmission apparatus #1 corresponding to the ingress node receives the reserve message and performs its corresponding cross connection processes (see arrow h of FIG. 17).
8. After advertisement operations by the transmission apparatuses are completed, all the transmission apparatuses within the network may recognize that the statuses of the bands used in route (1) are set to “determined (in use)”. Since route calculation involves searching “free” bands, the bands used in route (1) may no longer be considered for use in the route calculations performed by any of the transmission apparatuses after completion of such advertisement operations.
After forming route (1) shown in FIG. 16 as the active channel route, path establishing processes for forming a standby channel path are performed in order to enable immediate transmission of information via the standby channel route (substitute route) in a case where failure occurs in the active channel route. In the present example, paths along route (2) shown in FIG. 16 connecting the transmission apparatuses #1, #5, #6, and #4 in this order are established.
In Japanese Laid-Open Patent Publication No. 10-303932, a communication apparatus and a communication method are disclosed for performing resource allocation for communication requests transmitted from an unspecified number of sources according to their transmission information contents and dynamically changing resource allocation according to the information contents. According to the disclosed technique, an index indicating information contents attached to a message is used, and communication bands are assigned according to the index information. In this case, the communication band secured for transmitting information is managed by dividing the communication band into a fixed band and a dynamic band. The index is used to objectively determine priority of the communication requests according to the communication information contents and media characteristics when securing the fixed band and adjusting the dynamic band at the point of starting communication. Also, objective priority determination using the index is performed when executing communication reservation functions through scheduling in consideration of instances in which the fixed band or the dynamic band cannot be immediately secured. The data transmission procedures of servers and routers according to this technique, after performing data selection (e.g., index, size, transmission time, bandwidth) and issuing a user request (e.g., desired transmission start time/date), a router or a server determines priority of the fixed band for the requested data, and a terminal, a server, or a router arranged between a server and a terminal pre-reserves a communication channel from the transmission start time to the transmission end time. The pre-reservation involves accepting one or more communication requests over a predetermined bidding time period, determining priority of the communication requests if plural communication requests are received, pre-reserving bands for the communication requests according to the determined priority, registering the pre-reservations of the communication resources as actual reservations after the bidding time period is over, and notifying the user of the service start/end time.
According to the path establishing sequence performed in a conventional GMPLS network as is illustrated in FIG. 17, paths along route (1) connecting the transmission apparatuses #1-#4 in this order are established as the active channel route, and paths along route (2) connecting the transmission apparatuses #1, #5, #6, and #4 in this order are established as the standby channel route. In this case, bands of the paths forming route (2) may be exclusively reserved despite that fact that the paths of route (2) may not actually be used. In this respect, a method is proposed for establishing only route (1) and not establishing route (2) to realize efficient use of band resources. In this case, when failure occurs between the transmission apparatuses #3 and #4, for example, the transmission apparatus #3 transmits a warning message to the transmission apparatus #1 corresponding to the ingress transmission apparatus of route (1). Upon receiving the warning message, the transmission apparatus #1 executes signaling by performing route calculation once again to obtain a detour route so that traffic may be transmitted via route (2). However, in this case, the standby channel route may not always be secured; that is, another path may already be established using the band resources of the paths for forming route (2) in which case the desired transmission operations cannot be performed. Also, time may be required for performing the detour route recalculation processes and the signaling processes.
The technique disclosed in Japanese Laid-Open Patent Publication No. 10-303932 involves pre-reserving bands for a predetermined time period (bidding time period) and then actually reserving the bands after the predetermined time period elapses. This technique is similar to the above-described technique for reserving the bands to be used by an active channel route of a GMPLS network and securing the bands upon determining the active channel route as opposed to a technique for reducing unnecessary reservation of bands to be used by a standby channel route.